JPS62283372A - Separating device for transfer agent of image forming device - Google Patents

Abstract

PURPOSE:To attain stable separation by placing a moisture absorbing member that lowers resistance by moisture absorption to which bias is applied homopolar with a separating electrode near the separating electrode attached to a separating device. CONSTITUTION:A moisture absorbing member 6, for instance paper, that becomes low resistance by absorbing moisture is provided at a proper place of an insulating member near the tip of a separating electrode 5, and the member 6 is connected to a high voltage power source 8. In highly humid environment, resistance of the moisture absorbing member 6 is made low, and accordingly, potential is raised by voltage applied by the power source 8 and distribution of electric field between the back charge of a transfer agent P and the separating device 4 is disturbed, and corona discharge between the transfer agent P and separating electrode 5 is suppressed and leakage of charge is checked. Thus, deterioration of picture quality such as omission of transfer etc. can be prevented. When potential of the moisture absorbing member 6 is much lower than that of the separating electrode 5, the electric field is concentrated at the tip of the electrode. Thereby, corona discharge is easily generated, and separation of the transfer agent is made effectively.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (1) Purpose of the Invention (Industrial Field of Application) This invention relates to an image forming apparatus using an electrostatic transfer process such as an electrostatic copying machine and a printer; In particular, it relates to the transfer material separation device.

(Prior art and issues to be solved) A transferable image formed by charged toner on the surface of an image carrier,
Image forming apparatuses that include a process of bringing a transfer material, mainly paper, into contact with each other and transferring a toner image onto the transfer material by the action of a transfer charger, and then separating this transfer material from an image carrier have been well known. It is.

In this type of device, in order to transfer the toner image to the transfer material, a transfer charger applies a charge of opposite polarity to the toner to electrostatically transfer the image, so the transfer material is transferred after the transfer. tends to stick to the image carrier, and therefore, it is necessary to actively separate the transfer material from the image carrier at the post-transfer position.

Conventional separation means for this purpose include those that use mechanical means such as separation claws and chopstick belts, those that use air flow, and those that use a transfer charger to neutralize the electric charge applied to the transfer material during transfer. A number of proposals have been made, including a curvature separation method in which the transfer material is given a large curvature near the object or transfer site, and then separated by 1° using the elasticity or weight of the transfer material itself, each of which has its advantages and disadvantages. However, it has had some effect.

On the other hand, in recent years, smaller and more compact image forming apparatuses have come into use, and from this point of view, the above-mentioned curvature separation means is preferable because it does not require any special additional mechanism. However, on the other hand, this product has the disadvantage that it tends to cause 5-separation defects when the transfer material is thin and is sensitive to stiffness.

Therefore, in order to avoid such drawbacks, an extremely small separation electrode formed in the shape of a needle or plate is arranged downstream of the transfer charger when viewed in the direction of transfer of the transfer material, and is arranged in the opposite direction to the transfer corona. A structure has been proposed in which the charge on the transfer material is removed by applying a bias voltage lower than the voltage at which self-discharge starts depending on the polarity.

With this configuration, it is possible to obtain a small and compact separating device without damaging the photoreceptor or disturbing the toner image, as in the case of the above-mentioned separating charger. Even so, the characteristics of paper, which is most commonly used as a transfer material, vary significantly depending on the environment, especially the humidity, so that suitable results may not be obtained in all cases.

In other words, in a low-humidity environment, one sheet of paper has a high resistance and retains charge well, so it has a strong adsorption force to the image carrier after transfer, and in order to separate this, the bias voltage applied to the two separate electrodes must be increased. On the other hand, in a high-humidity environment, the transfer paper has a low resistance, making it easier for the charge to move, so that the charge applied by the transfer charger is transferred through the transfer material when the separation electrode is discharged. ! There is a risk that the electric field will leak to the electrodes, making it impossible to obtain sufficient electric field strength for transfer, resulting in transfer defects such as transfer omissions. In order to prevent this, it was necessary to keep the bias voltage of the separation electrodes low.

In order to avoid such inconveniences, it is immediately possible to detect the environmental humidity, the resistance value of the transfer material, etc. in advance, and control the discharge current of the molecule a electrode based on this. It will be readily understood that this requires additional mechanisms such as a detection means and a control circuit, making the device large and complicated, which goes against the demand for miniaturization and is impractical.

The present invention was designed to deal with such a situation, and provides a small and compact transfer material separation device that can always provide good transfer and separation effects regardless of the environment or the characteristics of the transfer material. The purpose is to

(2) Structure of the Invention (Technical Means for Solving the Problems and Their Effects)-1- In order to achieve the above-mentioned objects, the present invention provides an image forming apparatus that utilizes the above-mentioned static 7E transfer process. As seen from the charger, a separate electrode is disposed on the downstream side in the traveling direction of the transfer material, and a hygroscopic substance whose resistance value decreases due to moisture absorption is disposed near the separation pole. The device is characterized in that a bias having the same polarity as the separation electrode is applied continuously or intermittently so as to be effective in suppressing discharge of the separation electrode in a container in a low-humidity environment.

With this configuration, it is possible to respond to changes in the characteristics of the transfer material due to changes in the environment, and to suppress the discharge of the separation electrode only at the time when it is most needed.

(Description of an Embodiment) FIG. 1 is a side view of a main part showing an embodiment in which the present invention is applied to a copying machine equipped with a rotating cylindrical image bearing member (referred to as a photoreceptor) 1. As the photoreceptor rotates, the toner image formed on the surface of the rotating photoreceptor reaches the transfer site where the transfer charger 3 is located, and is transferred to the transfer paper (unloaded) that is fed in the direction of arrow B through the conveyance path 2. (shown in the figure) at the same timing, and is transferred onto the transfer paper by the action of the charge applied by the charger 3.

As is well known, around the photoreceptor there are a main charger for uniformly charging the photosensitive layer on the surface of the photoreceptor, an image information recessing means for forming an electrostatic latent image on the main charger, and an image information recessing means for forming an electrostatic latent image on the main charger. It goes without saying that a developing device for making a latent image visible, a cleaning device for removing residual toner, a residual charge removing means, etc. are provided, but these are not directly related to the present invention and will therefore be omitted. be.

Adjacent to the transfer charger 3, a pair of insulating members 4a, 4
A separation device 4 having a separation electrode 5 and a separation electrode 5 sandwiched therebetween are closely arranged.

The separation electrode 5 is made of a needle-like member or a metal whose edge on the side facing the transfer material is formed into a sawtooth shape.

It is made of a conductive plate and is connected to a high voltage power source 7.

Further, a moisture absorbing member 6, such as paper, which lowers the resistance by absorbing moisture, is disposed near the tip of the electrode 5 at a suitable location on the insulating member, and this member is connected to a high voltage power source 8. It is.

With this configuration, in a high-humidity environment, the resistance of the moisture absorbing member 6 is reduced, so that its potential increases with the voltage applied by the power source 8, and therefore, the transfer material P The electric field distribution between the backside charge and the separation device 4 is disturbed as shown in the second figure, and the roller discharge between the transfer material and the separation electrode is suppressed, preventing charge leakage and preventing transfer omissions, etc. Deterioration of image quality can be prevented.

In a low-humidity environment, the resistance of the moisture absorbing member 6 increases to the point where it is in an insulating state, so when a voltage is applied to it by the power supply 8, a large resistance value determined by the resistance value, static Mj, and capacitance of the moisture absorbing member 6 increases. The potential will rise slowly according to the time constant.

When the potential of the moisture absorption member 6 is much lower than that of the separation electrode, the electric field becomes concentrated at the tip of the electrode, as shown in FIG. Corona discharge is easily generated between the two, and the transfer material is effectively separated.

Furthermore, the separation effect can be made even more effective by applying the voltage to the moisture absorbing member 6 intermittently only during the time when the transfer process is complete and the separation effect is effective on the transfer material that has arrived at the position of the separation electrode. This means that it can be carried out in a practical manner.

Next, an experimental example of the present invention will be explained.
Using a ++a cylindrical photoreceptor as one separate electrode, the edge on the side facing the transfer material was placed at a south height of 3cm and a pitch of 1mm.
25+a+
This was placed at a position downstream of m, and at the same time, a piece of paper with a width of room was used as a moisture absorbing member and was attached to a position within a distance of 1 to 21 II l from the serrated tip of the separation electrode.

Using a separation device like the one above, the process speed is 50 mm.
/Sec (A size copy speed 6 fall/min), transfer corona voltage -5.3 KV, separation electrode bias voltage +3.
5 KV, moisture absorption member bias voltage +2.8 XV,
Copying was carried out with the moisture absorbing member bias voltage intermittently turned on for 6 seconds and off for 4 seconds, and the results showed that in a wide humidity range from low humidity to high humidity, various transfer materials from thin paper to thick paper to OHP paper could be copied. Stable separation was possible without any deterioration in image quality such as transfer omissions.

FIG. 4 shows another embodiment of the present invention, in which the molecule iTL
Since the polarity of the voltage applied to the pole and the moisture absorbing member is the same, a common power source 9 is used as a power source for both, thereby saving space and reducing costs.

FIG. 5 shows still another embodiment of the present invention, in which a suction member 78 and a separation electrode are provided between the insulating members 4a and 4b.
O is sandwiched between the two, the high voltage power source is shared, and the wiring is also simplified.

The separation electrode is not limited to a plate-shaped electrode as described in -1-, but it is of course possible to use a needle-shaped electrode or a thin wire stretched thereon. In addition to paper, various other materials such as cellophane, synthetic fibers, polymeric substances, and ceramics can be used as the moisture absorbing member. Furthermore, a hygroscopic substance may be applied as a paint to the very vicinity of the molecule aTL.

(3) Effects of the Invention Since the present invention has the configuration described above, it has an extremely simple, small and compact configuration, and can be used over a wide range of humidity changes, and is capable of handling images such as transfer omissions, etc. on various transfer materials. The effect is to perform stable separation without causing deterioration.

[Brief explanation of drawings]

FIG. 1 is a side view of essential parts showing an embodiment in which the present invention is applied to a copying machine. Second. FIG. 3 is an explanatory diagram showing the operation of the splitting head according to the present invention, FIG. 4 is a side view showing another embodiment of the present invention, and FIG. 5 is a side view showing still another embodiment. lψ...photoreceptor, ? . . . Φ conveyance path, 3. fist φ transfer charger, 4. minute # device, 5. separation electrode, 6. moisture absorbing member. 1 boar, 22,・'

Claims (2)

[Claims] (1) A transfer material is brought into contact with the toner image formed on the surface of the image carrier, the toner image is transferred to the transfer material by the action of a transfer charger, and then a separation device disposed adjacent to the transfer charger is used to transfer the toner image to the transfer material. In the image forming apparatus, a moisture absorbing member is arranged near the separation electrode disposed in the separation device to which a bias of the same polarity is applied and whose resistance decreases due to moisture absorption. A transfer material separation device. (2) The transfer material separation device according to claim 1, wherein a bias is intermittently applied to the moisture absorbing member.